The present invention relates to amorphous silicon semiconductor devices and more particularly to hydrogenated amorphous silicon devices having thin insulating oxide layers electrochemically grown by anodizing a surface of the silicon body.
The use of an insulating layer for altering the junction forming characteristics of semiconductor materials is well known in the art of crystalline semiconductor materials such as single crystal silicon. A relatively thin insulating oxide layer is generally interposed between the semiconductor body and a junction forming material. The thin oxide layer is sufficient to alter the materials' junction forming characteristics yet concurrently permit conduction through the insulator by electron or hole tunneling through the oxide. The term tunneling, as known to those of the art, refers generally to the ability of a charge carrier (electron or hole) under the influence of an electric field to pass through a narrow insulating region to allowable energy levels on the far side of the junction even though these charge carriers have insufficient energy to surmount the barrier formed between the insulator and the semiconductor material.
Thicker oxide layers are used in "field effect devices" where the oxide forms the dielectric in induced charge field controlled conduction in a semiconductor.
These oxide layers are conventionally either grown from the surface of the semiconductor or deposited onto the semiconductor from an extrinsic source. The term "grown" collectively represents the varied technique for oxidizing a surface region of the semiconductor material. The present invention teaches a technique for the electrochemical growth of an oxide layer from the surface of hydrogenated amorphous silicon.